黑河流域水循环过程中地下水同位素特征及补给效应

ISOTOPIC CHARACTERISTIC AND RECHARGE EFFECT OF GROUNDWATER IN THE WATER CIRCULATION OF HEIHE RIVER BASIN

通过环境同位素及其Tamers、IAEA模型应用研究表明,黑河流域水循环过程中地下水同位素特征与补给源属性和数量密切相关,具有非均一性;东部以山区降水通过出山地表径流补给为主,西部冰川雪融水和山区基岩裂隙水是主要补给源,下游区依赖中游区河水下泄状况,蒸发特征明显。东部同位素较新且地下水更新较快,西部同位素较老且地下水更新较慢;祁连山前戈壁带地下水同位素与山区河水相近,细土平原带地下水补给河水;高台一带受酒泉低氚值地下水补给影响而河水和地下水氚值都偏低;近河道带地下水年龄较新,远离河道则较老。因此,充分利用地下水与地表水之间转化规律,联合优化调控,有利于该区地下水资源可持续利用。

Field investigation and studies with the environmental isotopic way and with Tamres model and IAEA model, indicate that the variation of groundwater isotopic characteristics is related closely to the property and quantity of the recharge resources to groundwater in Heihe river basin of the Northwest internal region. In the basin, the shallow groundwater age is younger and its renewable rate is greater on the Gobi zone under Qilian mountains than that in the fine soil zone or the lower reaches. The shallow groundwater age is younger and its renewable rate is greater in the eastern area of the middle reaches than that in the western area, because the main recharge resource of groundwater is the rain of the Qilianshan mountain area in the eastern area of the middle reaches and is the snowmelt and the crevice groundwater from the mountain area in the western area. The age of shallow groundwater is less than 40 years in the eastern area of the middle reaches and that in the western area is greater than 40 years. The age of the confined groundwater is less than 1000 years in the eastern area of the middle reaches and that in the western area is greater than 1000 years. The age of most of the confined groundwater in the lower reaches is greater than 5000 years.The groundwater renewable rate near the riverbed is greater than that far from the riverbed. Above change characteristic is from the climatic variation and human activities that have important impacts on groundwater circulation and regeneration-evolution in the Heihe river drainage area of northwest endortheic drainage region. The shallow groundwater in the plain is mainly recharged by modern water. Some 35% of it is recharged by surface runoff transformed from bedrock fissure water of the Qilian mountains and the rest is recharged by infiltration of precipitation and melt water in the piedmont Gobi belt, both of which have strong regeneration ability. The confined groundwater mainly originates by recharge of regional meteoric water and river water in the geological history, which has relation with modern water circulation. The influence of human activities in the middle reaches of the river is an important factor responsible for the weakening of the groundwater recharge ability, sustained lowering of groundwater level and eco-environmental degradation in the lower reaches. Therefore, it is beneficial to groundwater resources sustainable utilization in regulation together with surface water that follows the natural regular of the transform of groundwater and surface water each other.